1. Field of the Invention
The present invention relates to an apparatus and method for processing a substrate, and more particularly to an apparatus and a method for processing a substrate to form a thin film of high-dielectric or ferroelectric such as barium/strontium titanates, or a copper film for wiring on the substrate, or to etch the substrate.
2. Description of the Related Art
Recently, in the semiconductor manufacturing industry, the integration of integrated circuits has been improved remarkably, and the research and development activities of DRAM are being intensively carried out in anticipation of gigabit order DRAMs which will replace current megabit order DRAMs. The capacitor element having a large capacity per unit area is needed to produce such DRAMs. As a dielectric thin-film material for producing elements having such a large capacity per unit area, in place of silicon oxide or silicon nitride having a dielectric constant of less than 10, a metallic oxide film material such as tantalum pentaoxide (Ta2O5) having a dielectric constant of approximately 20, or barium titanate (BaTiO3) or strontium titanate (SrTiO3) or barium strontium titanate having a dielectric constant of approximately 300 is considered to be a promising thin-film material. Further, a ferroelectric material having a higher dielectric constant is also considered to be a promising thin-film material.
In addition to the above, as a wiring material, copper which has a value of resistance lower than aluminum and a superior resistance against electromigration is considered to be a promising material. As a material for gate insulating film, BiVO, Bi4Ti4O12, YMnO3, ZnO, ZnS, and CdS are considered to be promising materials. As an electrode material having a perovskite structure, SrRuO3, BaRuO3, IrO, and CaRuO3 are considered to be promising materials. As a material for a barrier layer or a buffer layer, MgO, Y2O3, YSZ, and TaN are considered to be promising materials. As a superconductivity material, Laxe2x80x94Baxe2x80x94Cuxe2x80x94O, Laxe2x80x94Srxe2x80x94Cuxe2x80x94O, Yxe2x80x94Baxe2x80x94Cuxe2x80x94O, Bixe2x80x94Srxe2x80x94Caxe2x80x94Cuxe2x80x94O, Tlxe2x80x94Baxe2x80x94Caxe2x80x94Cuxe2x80x94O, and Hgxe2x80x94Baxe2x80x94Caxe2x80x94Cuxe2x80x94O are considered to be promising materials.
Processes for forming films of the above materials include plating, sputtering, chemical vapor deposition (CVD), and the like. The CVD process is expected to be most favorable for forming films as wiring having small widths. FIG. 9 of the accompanying drawings shows a substrate processing apparatus (chemical vapor deposition apparatus) for forming a thin film of high-dielectric or ferroelectric such as barium/strontium titanates, on a substrate. The substrate processing apparatus (vapor deposition apparatus) comprises a vaporizer (gas generator) 120 for vaporizing a liquid material, a hermetically sealable reaction chamber (processing chamber) 124 disposed downstream of the vaporizer 120 and connected to the vaporizer 120 through a material gas passage 122, and a vacuum pump 126 disposed downstream of the reaction chamber 124 and provided in an evacuation passage 128. An oxidizing gas pipe 130 for supplying an oxidizing gas such as oxygen is connected to the reaction chamber 124.
In the vapor deposition apparatus having the above structure, a substrate W is placed on a substrate holder 134 for holding and heating the substrate W, and a mixture of material gas and oxidizing gas is ejected over the substrate W from gas ejection ports 136 of a gas ejection head 138 while keeping the substrate W at a predetermined temperature, thereby depositing a thin film on a surface of the substrate W. In this case, it is necessary to supply the material gas stably to the substrate W in the reaction chamber 124. The material gas is produced by liquidizing Ba(DPM)2, Sr(DPM)2 or the like which is solid at room temperature, mixing the liquidized substance with organic solvent such as tetrahydrofuran (THF) for stabilizing vaporization characteristics, and vaporizing the obtained mixture by the vaporizer 120.
When a plurality of organic metal materials are used to form a film, the substrate processing apparatus tends to suffer certain problems. Specifically, since the organic metal materials have their inherent vaporization temperatures and decomposition temperatures, a temperature range in which the organic metal materials can exist stably in their vapor phase is generally narrow. A simple organic metal material gas which is mixed with the organic solvent cannot vaporize if the organic solvent vaporizes earlier. Therefore, it is necessary to vaporize the organic metal material gas and the organic solvent at the same time. If the material gas is subjected to a temperature irregularity while it is being supplied to the substrate, then the material gas is liable to be condensed or decomposed, and the temperatures of some of the organic metal materials have to be controlled so as to be lower than the vaporization temperature of any one of the materials.
For example, it is assumed that an organic metal material A has a vaporization temperature TKA and a decomposition temperature TDA, and an organic metal material B has a vaporization temperature TKB and a decomposition temperature TDB. If TKB less than TKA less than TDB less than TDA, then a temperature range in which the materials A, B can exist stably in their vapor phase is from TKA to TDB. If TKB less than TDB less than TKA less than TDA, then in order to suppress decomposition of the organic metal material B, the process temperature needs to be controlled so as to be equal to or lower than the vaporization temperature of the organic metal material A.
The inventors of the present application have found that the film growth rate and the substrate temperature are related to each other as shown in FIG. 10 of the accompanying drawings. As shown in FIG. 10, when the heater of the substrate holder heats the substrate W to a film growth temperature T1, the rate vs. temperature curve exhibits the reaction-limited in which the film growth rate increases in proportion to the substrate temperature until the film growth temperature T1 is reached, and the supply-limited in which the film growth rate is substantially constant beyond the film growth temperature T1. The material gas is introduced into the reaction chamber at a low temperature that is substantially the same as the vaporization temperature in order to suppress reaction and decomposition of the material gas, and an oxidizing gas for reaction with the material gas is also introduced at the same low temperature. Therefore, the surface of the substrate is held at a temperature T2 which is lower than the film growth temperature T1, with the result that the substrate processing apparatus cannot perform its maximum capability.
As semiconductor devices become more highly integrated, their structural details become finer, and a more uniform film needs to be deposited on their finer uneven surfaces. For example, as shown in FIG. 11 of the accompanying drawings, when a thin film 142 of high-dielectric or ferroelectric is grown in a minute hole or trench 140 (in some case stack structure is also available) defined in the surface of a semiconductor substrate W, coverage characteristics including the ratio of a film thickness B on the bottom of the groove 140 to a film thickness A on the surface of the semiconductor substrate W, i.e., the ratio B/A (bottom coverage), the ratio of a film thickness C on a side of the groove 140 to the film thickness A, i.e., the ratio C/A (side coverage), and the ratio of a film thickness C2 on an upper portion of the side of the groove 140 to a film thickness C1 on a lower portion of the side of the groove 140, i.e., C2/C1 (side coverage uniformity), are required to be increased.
For increasing the above coverage characteristics, a film may be grown according to the reaction-limited of an Arrhenius"" curve which represents the relation of the film growth rate and the reciprocal of the film growth temperature as shown in FIG. 12 of the accompanying drawings. If a film were grown according to the supply-limited, then, as shown in FIG. 13A of the accompanying drawings, the supply of particles (molecules) 144 of a material gas (film forming gas) would fail to catch up with the reaction, and the particles (molecules) 144 of the material gas would react and be deposited on a surface which they have first reached. As a result, the particles (molecules) 144 of the material gas become sparse in the groove 140, and the film growth in the groove 140 becomes smaller than the film growth on the surface of the substrate W, resulting in poor coverage characteristics. If a film is grown according to the reaction-limited, then, as shown in FIG. 13B of the accompanying drawings, the reaction of particles (molecules) 144 of the material gas fails to catch up with the supply of particles (molecules) 144, so that the probability of attachment of material gas particles (molecules) is low. Thus, a particle (molecule) 144 of the material gas does not contribute to film growth at a spot X which it has first reached, but is deposited at a next spot Y. Consequently, a film can be grown in the groove 140 according to the same film growth characteristics as on the surface of the substrate W, resulting in good coverage characteristics.
However, the reaction-limited (the supply of particles (molecules) is sufficient) is a phenomenon in which the reaction rate increases as the film growth temperature rises, and the supply-limited (the supply of particles (molecules) is insufficient) is a phenomenon in which the reaction rate is substantially constant regardless of a rise in the film growth temperature. Therefore, when a film is grown according to the reaction-limited, the film growth rate is lowered. Accordingly, the reaction rate and the coverage characteristics are correlated such that if one of the reaction rate and the coverage characteristics becomes better, the other becomes worse.
The substrate processing apparatus for processing substrates one by one are required to shorten a processing time per substrate in a processing chamber for thereby increasing the number of substrates processed per time by the apparatus. The processing time in the processing chamber is roughly divided into the following periods:
1) Heating period for heating a substrate (preheating time); and
2) Processing period for actually forming a film on a substrate or etching a substrate.
If the processing period 2) is essentially short as in a process of growing a copper film, then the length of the heating period (preheating time) 1) forms a bottleneck in increasing the throughput.
According to a conventional process for heating (preheating) a substrate in a processing chamber with a heating device, a substantial heat capacity is required to maintain temperature stability of the substrate. Inasmuch as a heater having a large time constant in increasing or reducing the temperature is generally used as the heating device, when the temperature of the substrate becomes close to a target temperature, the temperature difference between the substrate and the heating device (heater) is reduced, thus requiring a very long time for the substrate to reach the target temperature.
In order to improve the temperature rising characteristics of a substrate, the heating device may have a temperature adjusting device for setting a heating temperature of the heater higher than the target temperature of the substrate, and the temperature of the heater may be controlled to provide a large temperature difference when the substrate temperature becomes close to the target temperature, for thereby shortening the time required for the substrate to reach the target temperature. However, this scheme is also disadvantageous in that when the substrate temperature becomes close to the target temperature, it is necessary to effect temperature control to lower the temperature of the heater to reach the target temperature, and the heating process becomes time-consuming unless forced cooling is performed on the substrate.
It is therefore an object of the present invention to provide an apparatus and a method for processing a substrate which can form a film on the substrate using two or more film materials by stably supplying the film materials for an increased film growth rate.
Another object of the present invention is to provide an apparatus and a method for processing a substrate which can increase coverage characteristics while maintaining a high film growth rate.
Still another object of the present invention is to provide an apparatus and a method for processing a substrate which can heat the substrate uniformly and quickly in a processing chamber for an increased throughput.
According to an aspect of the present invention, there is provided an apparatus for processing a substrate, comprising a gas ejection head for individually introducing at least two gases including a material gas and ejecting the gases toward a substrate to be processed. The gas ejection head has at least two gas passageways for individually introducing the at least two gases, and at least two temperature control devices for individually controlling or maintaining temperatures of the gases flowing through the gas passageways.
With the above arrangement, the at least two gases including the material gas can individually be controlled or maintained in temperature irrespectively of each other and set to temperatures optimum for processing a substrate, e.g., forming a film on the substrate, and then can be ejected from the gas ejection head toward the substrate.
Each of the at least two gases contains at least two different organic metal materials. The gases containing the two different organic metal materials can individually be set to desired temperatures irrespectively of each other. The gases thus set to the desired temperatures do not react prematurely and are not decomposed in passageways. When the gases are finally mixed with each other, they can be kept at a higher temperature for an increased film growth reaction rate.
One of the at least two gases comprises a high-temperature gas containing at least one of an oxidizing gas, N2, and an inert gas. When oxides such as BST, Y1 or PZT are deposited on the substrate, the material gas ejected from the gas ejection head can be heated by the high-temperature gas containing at least one of an oxidizing gas, N2, and an inert gas, so that the temperature of the mixture of the gases can be made close to a temperature of about 450xc2x0 C. optimum for film growth.
In the case where oxygen is contained in a material gas used for forming a film, in place of an oxidizing gas, a process in which a gas such as N2 gas or an inert gas is heated to a high temperature and mixed with the material gas is considered.
One of the at least two gases comprises a high-temperature gas containing at least one of a reducing gas, N2, and on inert gas. When metals such as copper are deposited, the material gas ejected from the gas ejection head can be heated by the high-temperature gas containing at least one of a reducing gas, N2, and an inert gas, so that the temperature of the mixture of the gases can be made close to a temperature optimum for film growth.
One of the at least two gases comprises a temperature-adjusting gas for heating the substrate and/or cooling the substrate. A gas passageway for the temperature-adjusting gas in the gas ejection head may be provided separately from a low-temperature gas passageway through which the material gas flows. With the gas passageway for the temperature-adjusting gas being provided independently of the gas passageway for the material gas, the effect of the temperature of the temperature-adjusting gas on the material gas is eliminated when the temperature-adjusting gas is replaced by the material gas, and these gases are prevented from being mixed together.
According to another aspect of the present invention, there is provided an apparatus for processing a substrate, comprising: a processing chamber having a gas ejection head for individually introducing at least two gases including a material gas and ejecting the gases toward a substrate to be processed, the gas ejection head having at least two gas passageways for individually introducing the at least two gases, and at least two temperature control devices for individually controlling or maintaining temperatures of the gases flowing through the gas passageways; a gas supply source for supplying the gases to the gas ejection head; and a substrate holder disposed in the processing chamber in confronting relationship to the gas ejection head.
According to still another aspect of the present invention, there is provided an apparatus for processing a substrate, comprising: a processing chamber for processing a substrate therein; a substrate holder disposed in the processing chamber, for holding and heating the substrate; and a temperature-adjusting gas introducing device for introducing a temperature-adjusting gas into the processing chamber to perform at least one of heating the substrate and cooling the substrate, in a predetermined position in the processing chamber.
Gases can easily be controlled so as to be turned on and off during their flow. A temperature-adjusting gas having a temperature higher than a target temperature may be used to heat a substrate. When the temperature of the substrate reaches the target temperature, the supply of the temperature-adjusting gas is stopped, or when the temperature of the substrate reaches a temperature close to the target temperature, a gas having a temperature close to the target temperature is supplied, for thereby heating (preheating) and/or cooling the substrate quickly to equalize the temperature of the substrate to the target temperature. The temperature-adjusting gas is preferably composed of an H2 gas or the like which has a large specific heat and thermal conductivity for shortening the period of time required to increase or reduce the temperature of the substrate. If an H2 gas poses a problem with regard to the process of forming films, then the temperature-adjusting gas may be an N2 gas or an inert gas.
If the substrate is cooled at a position spaced from the substrate holder, then the temperature of a heating mechanism combined with the substrate holder does not need to be varied. As a result, the substrate can be cooled quickly, and the period of time required for processing the substrate can be shortened for an increased throughput. The substrate may be heated while being placed on the substrate holder for higher efficiency due to the conduction of heat from the substrate holder. However, in order to avoid a heat shock to the substrate, the substrate is preferably heated above the substrate holder. If the substrate is heated above the substrate holder, then radiant heat from the substrate holder can also be utilized to heat the substrate, the substrate can easily be handled, and no extra space is required. Specifically, the substrate may be lifted off the substrate holder by pins combined with the substrate holder. By heating the substrate at this position, since the substrate is not affected by the temperature of the substrate holder, it is possible to perform heat treatment such as annealing of the substrate after forming a film at a temperature different from the temperature for forming the film by flowing a certain gas at a certain temperature. The pins may comprise pins that can project upwardly from the substrate holder, as used heretofore to deliver substrates.
A ring-shaped gas inlet pipe may be disposed in an upper space in the processing chamber, and the temperature-adjusting gas may be ejected from gas ejection ports defined in the gas inlet pipe at a given pitch in the circumferential direction of the gas inlet pipe. The ring-shaped gas inlet pipe allows a substrate processing apparatus which cannot have a gas ejection head due to structural limitations, e.g., a substrate processing apparatus for processing a substrate for ECR, to process the substrate in the manner described above.
According to yet another aspect of the present invention, there is provided a method for processing a substrate, comprising: individually controlling or maintaining temperatures of at least two gases including a material gas; and introducing the gases into a processing chamber.
Each of the at least two gases contain at least two different organic metal materials.
One of the at least two gases comprises a high-temperature gas containing at least one of an oxidizing gas, N2, and an inert gas.
One of the at least two gases comprises a high-temperature oxidizing gas containing at least one of a reducing gas, N2, and an inert gas.
The method further comprises introducing at least one of the at least two gases, excluding the material gas, into the processing chamber at a temperature which is equal to or lower than the temperature of the material gas. Therefore, the temperature of an additive gas, such as an oxidizing gas or a hydrogen gas other than the material gas, can be lowered without varying the temperature of the material gas which is unstable and liable to be condensed relatively easily, thus lowering the reactivity of at least one of the two or more gases that contribute to the reaction for improving coverage characteristics, and the substrate can be maintained at a high temperature for keeping a high film growth rate.
The method further comprises delivering the material gas and the gas to be introduced into the processing chamber at a temperature which is equal to or lower than the temperature of the material gas, without being mixed with each other, and mixing the material gas and the gas with each other in the processing chamber or prior to being introduced into the processing chamber.
The gas to be introduced into the processing chamber at a temperature which is equal to or lower than the temperature of the material gas has a temperature equal to or lower than a condensation temperature of the material gas. The material gas and the gas, such as an oxidizing gas, are prevented from being mixed with each other at an early stage while being delivered, and hence from separating out substances, and the material gas is also prevented from being condensed.
According to yet still another aspect of the present invention, there is provided a method for processing a substrate, comprising: introducing a material gas containing an organic metal material of titanium and a material gas containing another organic metal material into a processing chamber to deposit a thin film on a substrate; wherein the material gas containing the organic metal material of titanium has a temperature equal to or lower than the temperature of the material gas containing the other organic metal material.
An organic metal material of titanium (Ti) has a lower vaporization temperature than those of other organic metal materials of barium (Ba), strontium (Sr), etc., and can be delivered without condensation when individually lowered in temperature separately from the other organic metal materials and vaporized. When the temperature of only the titanium material is made lower than the temperature of the other materials, the reaction of the titanium material is delayed for improved coverage characteristics. BST is a solid solution of BTO and STO, and forms a film due to a reaction of between Ti and Ba, Ti and Sr. Consequently, the coverage characteristics can be controlled by controlling the temperature of the reaction of the Ti material.
The method further comprises delivering the material gas containing the organic metal material of titanium and the material gas containing the other organic metal material, without being mixed with each other, and mixing the material gas containing the organic metal material of titanium and the material gas containing the other organic metal material with each other in the processing chamber or prior to being introduced into the processing chamber.
According to a further aspect of the present invention, there is provided a method of processing a substrate, comprising: holding a substrate by a substrate holder in a processing chamber; and ejecting a temperature-adjusting gas toward said substrate to perform at least one of heating the substrate and cooling the substrate, in a predetermined position in said processing chamber.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.